Non-NMDA receptors in the nucleus of the tractus solitarius play the predominant role in mediating aortic baroreceptor reflexes

Gordon, Frank J.; Leone, Christina

doi:10.1016/0006-8993(91)91418-z

Cited by 89 publications

(34 citation statements)

References 12 publications

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“…The main transmitter released by primary baroreceptor afferent fibers within the NTS is glutamate, which excites second-order NTS neurons primarily via non-N-methyl-D-aspartate (non-NMDA) receptors (77). Second-order barosensitive neurons that terminate in the CVLM also release glutamate, which acts on NMDA receptors on the GABAergic inhibitory neurons that project to the RVLM (76).…”

Section: Central Baroreflex Pathways and Their Modulation By Hormonesmentioning

confidence: 99%

Pregnancy and the endocrine regulation of the baroreceptor reflex

Brooks

Dampney

Heesch

2010

American Journal of Physiology-Regulatory, Integrative and Comp

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-The purpose of this review is to delineate the general features of endocrine regulation of the baroreceptor reflex, as well as specific contributions during pregnancy. In contrast to the programmed changes in baroreflex function that occur in situations initiated by central command (e.g., exercise or stress), the complex endocrine milieu often associated with physiological and pathophysiological states can influence the central baroreflex neuronal circuitry via multiple sites and mechanisms, thereby producing varied changes in baroreflex function. During pregnancy, baroreflex gain is markedly attenuated, and at least two hormonal mechanisms contribute, each at different brain sites: increased levels of the neurosteroid 3␣-hydroxydihydroprogesterone (3␣-OH-DHP), acting in the rostral ventrolateral medulla (RVLM), and reduced actions of insulin in the forebrain. 3␣-OH-DHP appears to potentiate baroreflex-independent GABAergic inhibition of premotor neurons in the RVLM, which decreases the range of sympathetic nerve activity that can be elicited by changes in arterial pressure. In contrast, reductions in the levels or actions of insulin in the brain blunt baroreflex efferent responses to increments or decrements in arterial pressure. Although plasma levels of angiotensin II are increased in pregnancy, this is not responsible for the reduction in baroreflex gain, although it may contribute to the increased level of sympathetic nerve activity in this condition. How these different hormonal effects are integrated within the brain, as well as possible interactions with additional potential neuromodulators that influence baroreflex function during pregnancy and other physiological and pathophysiological states, remains to be clearly delineated.3␣-hydroxy-dihydroprogesterone; angiotensin II; insulin; paraventricular nucleus of the hypothalamus NORMAL PREGNANCY is characterized by profound changes in fluid and electrolyte balance and blood pressure regulation. Blood volume and cardiac output increase by 30 -50%, but arterial pressure falls due to even greater decreases in systemic vascular resistance (120,138,189). These hemodynamic alterations are evident early in pregnancy, precede the increases in uterine blood flow, and are sustained until parturition (127,138,189). Considerable data implicate increases in relaxin and nitric oxide (NO) in the systemic vasodilation induced by pregnancy (20,127,128,177,196). In addition, peripheral vascular sensitivity to circulating vasoconstrictors including vasopressin, angiotensin II (ANG II), and norepinephrine (NE) is decreased (50,71,154).Unlike the hemodynamic changes, which likely subserve adequate fetal development, an adverse consequence of normal pregnancy is a marked impairment of the arterial baroreceptor reflex. This change was first noted by Humphreys and Joels (97,98) in an extensive series of studies in anesthetized pregnant rabbits, in which reductions in carotid sinus pressure failed to elicit normal increases in arterial pressure and peripheral vascular resistanc...

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Section: Central Baroreflex Pathways and Their Modulation By Hormonesmentioning

confidence: 99%

Pregnancy and the endocrine regulation of the baroreceptor reflex

Brooks

Dampney

Heesch

2010

American Journal of Physiology-Regulatory, Integrative and Comp

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“…4,9 ␣-Amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA)-type glutamate receptors 10 are involved in mediating the effects of baroreceptor stimulation within the NTS. [11][12][13] Recent studies have shown that 3 of the 4 known AMPA receptor subunits are present within the NTS. 14,15 We have found similar results, 16 and we also noted that the GluR1 subunit was most heavily located in dendritic spines, suggesting a potential role for AMPA receptors containing this subunit in synaptic plasticity within the NTS.…”

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confidence: 99%

Structural Changes in AMPA-Receptive Neurons in the Nucleus of the Solitary Tract of Spontaneously Hypertensive Rats

2003

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Abstract-The baroreceptor reflex is critical for homeostatic regulation of blood pressure and is initiated centrally by glutamate release from baroreceptive afferents onto neurons in the nucleus of the solitary tract that activates AMPA-type glutamate receptors. The GluR1 subunit of the AMPA receptor is located at postsynaptic sites within the nucleus of the solitary tract, particularly in dendritic spines, which are important sites for synaptic plasticity. We tested whether the distribution of GluR1 changes after sustained hypertension, which alters baroreceptor afferent activity. We examined the distribution of GluR1 in the nucleus of the solitary tract of both hypertensive (spontaneously hypertensive) and normotensive (Wistar-Kyoto) rats at the light microscopic and electron microscopic levels. There were more GluR1-containing dendritic spines in the nucleus of the solitary tract of hypertensive rats compared with normotensive rats, which was attributable to an increase in the proportion of dendritic spines containing GluR1 as well as an increase in the total number of dendritic spines. The differences were only seen after the development of hypertension and were not seen in rostral regions of the nucleus of the solitary tract. In the spontaneously hypertensive rat, many synapses on GluR1-containing dendrites had the morphological features of synapses undergoing dynamic changes, including the presence of perforated synapses. These results suggest that changes in afferent activity to the nucleus of the solitary tract during sustained hypertension alter both the dendritic structure and AMPA receptor content of some neurons. These structural changes may be a substrate for central resetting of the baroreceptor reflex. Key Words: rats, spontaneously hypertensive Ⅲ rats, inbred WKY Ⅲ central nervous system Ⅲ blood pressure Ⅲ baroreflex Ⅲ glutamate receptor B aroreceptors are stretch receptors found in large blood vessels around the heart. Activation of these receptors is relayed to the brain by afferents to the nucleus of the solitary tract (NTS), 1 which release glutamate. 2,3 A central reflex arc through the brain stem and spinal cord serves to return blood pressure to homeostatic values. Although the underlying of hypertension is likely to be heterogeneous, at least some forms of hypertension may be caused by, or lead to, dysfunction within the central baroreceptor reflex arc. 4,5 Functional changes in properties of NTS neurons as well as altered blood pressure responses to glutamate microinjections into this region have been reported during hypertension. 6 Although it has been postulated that changes in central autonomic neurons may occur during hypertension, 7,8 these changes have been difficult to confirm. 4,9 ␣-Amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA)-type glutamate receptors 10 are involved in mediating the effects of baroreceptor stimulation within the NTS. [11][12][13] Recent studies have shown that 3 of the 4 known AMPA receptor subunits are present within the NTS. 14,15 We have found simil...

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“…Indeed, glutamate microinjected into the NTS induces depressor and bradycardic responses in anesthetized rats (4,12,33). Although recent reports suggest that NMDA and metabotropic glutamate receptors are also involved, non-NMDA receptors are probably the primary mediators of the aortic baroreflex (34). On the other hand, it was reported that there exist neurons that may contain DOPA as an end product, i.e., DOPApositive and dopamine-negative or TH-positive and AADC-negative neurons in the NTS (8,9,21).…”

Section: Dopaergic Relay In the Lower Brainstemmentioning

confidence: 99%

The Cardiovascular Actions of DOPA Mediated by the Gene Product of ocular albinism 1

et al. 2014

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Abstract. l-3,4-Dihydroxyphenylalanine (DOPA) is the metabolic precursor of dopamine, and the single most effective agent in the treatment of Parkinson's disease. One problem with DOPA therapy for Parkinson's disease is its cardiovascular side effects including hypotension and syncope, the underlying mechanisms of which are largely unknown. We proposed that DOPA is a neurotransmitter in the central nervous system, but specific receptors for DOPA had not been identified. Recently, the gene product of ocular albinism 1 (OA1) was shown to possess DOPAbinding activity. It was unknown, however, whether or not OA1 is responsible for the actions of DOPA itself. Immunohistochemical examination revealed that OA1 was expressed in the nucleus tractus solitarii (NTS). OA1-positive cells adjacent to tyrosine hydroxylase-positive cell bodies and nerve fibers were detected in the depressor sites of the NTS. OA1 knockdown using oa1-specific shRNA-adenovirus vectors in the NTS reduced the expression levels of OA1 in the NTS. The prior injection of the shRNA against OA1 suppressed the depressor and bradycardic responses to DOPA but not to glutamate in the NTS of anesthetized rats. Thus OA-1 is a functional receptor of DOPA in the NTS, which warrants reexamination of the mechanisms for the therapeutic and untoward actions of DOPA.

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Non-NMDA receptors in the nucleus of the tractus solitarius play the predominant role in mediating aortic baroreceptor reflexes

Cited by 89 publications

References 12 publications

Pregnancy and the endocrine regulation of the baroreceptor reflex

Pregnancy and the endocrine regulation of the baroreceptor reflex

Structural Changes in AMPA-Receptive Neurons in the Nucleus of the Solitary Tract of Spontaneously Hypertensive Rats

The Cardiovascular Actions of DOPA Mediated by the Gene Product of ocular albinism 1

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